google closure compiler - Javascript minification of comparison statements

Question

I was looking over one of the minified js files generated by closure. I found that wherever I'm checking for equality between a variable and string like,

a == "13" || a == "40"

closure replaces it with

"13" == a || "40" == a

Why is this modification done? Is there some performance advantage here?

Answer 1

This is done as for a minor gzip compression advantage. If you have "x == 1" and "1 == x" the compiler switches it to "1 == x" in both cases and you get more regular code that compresses better. The win is so minor, that I've considered deleting the code and saving the cpu cycles, but it is on for now. It has nothing to do with preventing programmer errors as it will never switch "x = 2" into "2 = x" as that would change the meaning of the program.